Jules Verne understood it best: you can fly around the world in 80 days and dive 20,000 leagues under the sea, but you can also find awesome otherworldly adventures right beneath your feet.

Just ask the Mexican miners who discovered a sweltering cavern filled with crystals as tall as apartment buildings, or the Brazilians who first gazed into Poço Encantado, a cave with a lake so clear you lose all sense of perspective looking into its depths. Mother Nature knows what she’s doing when it comes to creating cool underground attractions.

Mankind isn’t so bad at it either. Turkey’s ancient city of Derinkuyu is thought to have housed 20,000 people 18 stories inside a mountain. And in Luxor’s Valley of the Kings, the Tomb of Seti I’s sheer size and extensive Book of the Dead bas-reliefs would make any aspiring Egyptologist cry mummy.

Closer to home, a Cold War bunker in rural West Virginia offers a peek into a different sort of afterlife. Luckily, American congressmen never had to use the top-secret hideaway (even if it was hidden beneath a luxury hotel)—unlike London’s Cabinet War Rooms, another man-made sights turned must-visit museum for cultural spelunkers.

Ready to discover some of the earth’s coolest underground sights? Here’s where to start digging.